Here are the data structures with brief descriptions:

a_stream
hashbucket
hashentry
psi_arg
psi_feature
text_buffer
wl_Arc
wl_choice_point
wl_definition
wl_DisplayElt
wl_EventClosure
wl_goal
wl_GraphicClosure
wl_hash_table
wl_int_list
wl_item
wl_keyword
wl_Line
wl_ListHeader
wl_ListLinks
wl_module
wl_node
wl_operator_data
wl_pair_list
wl_parse_block
wl_Polygon
wl_PostScriptClosure
wl_psi_term
wl_Rectangle
wl_resid_block
wl_resid_list
wl_residuation
wl_stack
wl_String
wl_tab_brk
wl_triple_list